In their experiments, the researchers first showed users wearing the mind-control headsets a series of known images and numbers to measure what a moment of recognition looked like in their EEG data, using the P300 response, a electrical spike that typically appears close to 300 milliseconds after a stimulus the subject recognizes.

Then they showed the subjects a series of test images and numbers and looked for those same signals. In a collection of unknown faces, for instance, they found a significant spike in the EEG data for a picture of Barack Obama that revealed the test subjects’ recognition of the president’s face.

A P300 event-related potential elicited as a brain response to a target stimuli (in this experiment the non-target stimuli were pictures of unknown faces, while the target stimuli was the picture showing President Obama) (credit: Ivan Martinovic et al)

When shown a collection of locations on maps that included one of their home, the headset-wearers’ brains emitted tell-tale hints that allowed the experimenters to determine their home’s general location with 60% accuracy on the first try among a collection of ten choices.

And when the subjects were asked to memorize a four-digit PIN and then shown a series of random numbers, the researchers found they could guess which of those random numbers was the first digit in the PIN with about 30% accuracy on the first try–far from a home run, but a significantly higher success rate than a random guess.